A running system of a motor vehicle comprises a vehicle frame, axles, suspensions, and wheels, wherein the vehicle frame is an important part of basic members and the running system of the motor vehicle; a power assembly of the motor vehicle and various assemblies of a chassis thereof are all installed onto the vehicle frame; also, the vehicle frame is a base for supporting carriage, and is required to have enough stiffness and appropriate flexibility which may have a key influence on the performance of the whole vehicle. An existing frame structure of a motor vehicle still follows principle of the model T (ladder frame), where front and rear axles (a bridge rack, a portal axle, and the like) serving as cross sections and vehicle beams serving as longitudinal sections are hinged by using leaf springs to form a vehicle frame that supports and receives the loads of an chassis and the whole vehicle, and the supporting, transmission and location functions of the axles are still not changed. Such a structure is simple, and good in manufacturability, but has the disadvantages of high weight, high vehicular center of gravity, occupancy of much central position, and the like. Although the frames of a monocoque bus and a platform frame car in modern times have no such disadvantages, the arrangement of assemblies is still limited. With the development of electrification, intelligentization and lightweight, it also calls for the emergence of new vehicle frames meeting the requirements.
The existing vehicle frames are mainly divided into the following several types according to different structures: first, a crossbeam type structure, including a backbone type, a side beam type, and a comprehensive type, and mainly applied to buses and trucks; second, a platform frame that is shaped once and suitable for integrated mass production of cars; and third, a space type (steel tube type) monocoque structure that is mainly applicable to large buses, less in such forms as an IRS type and a semi-frame type.
However, the three ways all have the following major disadvantages: for the crossbeam type structure, front and rear axles serve as the cross sections and longitudinal beams are spanned over the axles, resulting in occupancy of most middle space of the vehicle body and difficulty lowering of the height of the center of gravity with the width of the vehicle frame being restricted by numerous factors. For the platform vehicle frame, bridge racks are set up as supports; high technical requirements are made on longitudinal framework connections and lateral integrated shaping connections; one vehicle model requires one mold, and the production process is complicated with high remodeling costs. For the space type monocoque vehicle frame, a crossbeam is decomposed into a plurality of trusses, resulting in occupancy of the overall space and increase of the vehicle body height. Such a vehicle frame also has the disadvantages of complicated design, numerous parts, strict requirements on the technical process, high production costs, numerous weld joints, and reduction of the allowable stress.
In patent applications including publication No. CN103381851A, published on Nov. 6, 2013 and entitled “ELECTRIC VEHICLE CHASSIS”, and publication No. CN1631690A, published on Jun. 29, 2005 and entitled “ELECTRIC VEHICLE CHASSIS WITH INDEPENDENTLY-SUSPENDED AND INDEPENDENTLY-DRIVEN REAR WHEELS”, the integrated vehicle frames presented therein both follow principle of ladder frame with partial improvements, but no new axleless structure is achieved in any one of them; in addition, the requirements on the electric, lightweight and intelligent functions are also not well met.